The kin selection hypothesis is a theory that explains altruistic behavior in which individuals help their kin to protect and spread their genes. Using the examples of honeybees and meerkats, we will explore the applicability and limitations of this hypothesis, discussing the complexity of altruistic behavior and the need for different approaches.
What do humans, bees, and meerkats have in common? They all live in families, kinship communities, and are capable of altruistic behavior, such as personal sacrifice, for the benefit of others. According to a recent Yonhap News Agency report, eight out of 10 pregnant women diagnosed with cancer do not give up on giving birth. Even though chemotherapy during pregnancy is limited and poses a very dangerous obstacle to the mother’s health, they sacrifice themselves out of maternal love to protect their unborn child. When you read newspaper and internet articles, you often come across cases like this, where individuals within a family sacrifice themselves to protect other family members. It’s also a common theme in movies and dramas, where the main character sacrifices themselves for their family. Because it’s a familiar theme, it’s often very emotional and resonates with people. The kin selection hypothesis is a hypothesis that explains why these altruistic behaviors among kinship communities can occur and why these individuals have been able to survive. So, what exactly is the kin selection hypothesis, what species’ behaviors support it, and what are the limitations of using this theory alone to explain altruistic behavior in organisms?
When explaining altruistic behavior among kin, the kin selection hypothesis does not speak from the perspective of an individual whose primary goal is to survive, but rather from the perspective of a gene within an individual whose primary goal is to reproduce. Individuals are the vessel, genes are the contents. The hypothesis of kin selection explains that the contents of a vessel tell its genes to behave as they do, even if it means sacrificing some of their own, if there is more to be gained by protecting other vessels containing the same contents as theirs. In other words, an act that seems altruistic because it sacrifices itself from the perspective of an ‘individual’ is explained as a selfish act from the perspective of a ‘gene’ that wants to preserve and reproduce its own kind. This explanation allows us to see why altruistic individuals can thrive in a way that Darwin’s “survival of the fittest” could not explain. Darwin’s idea was that the organisms that had the best chance of surviving in their environment would thrive. This is “survival of the fittest. The survival of the fittest could not explain the survival of altruistic individuals, because altruistic individuals would be at a disadvantage. However, with the advent of the hypothesis of kin selection, the altruistic behavior of organisms, which could not be explained in terms of individual individuals aiming to survive, was clearly explained through the lens of genes. Thus, the survival of altruistic individuals could be explained.
Now, let’s take a look at the altruistic behaviors that support the kin selection hypothesis. We can think of bees as an example of altruistic behavior that we can easily observe around us. The principle of survival of the fittest does not explain the altruism of worker bees, who sacrifice their own reproduction. However, this problem is solved when we shift our perspective from individuals to genes. Gene sharing, a measure of the extent to which individuals in a bee colony share the same genes, is as high as 50% for queens and their children and 75% for queens and workers of the same generation. In addition, for the queen and worker bees of the same generation, the gene sharing between the queen’s eggs and the worker bees is 50%, which is the same as the worker bees reproducing on their own. In this situation, each gene is replicated without the need for all females to reproduce. As a result, the division of labor allows the queen to lay eggs and the worker bees to raise the eggs laid by their sister queen, and dedicating themselves to work rather than reproduction can be an efficient way to increase the chances of preserving genes like their own within the bee colony. The selfish aspect of the ‘gene’ explains the altruistic behavior of individuals like this.
To continue with the human example, altruistic behavior between siblings can also be explained as an example of the kin selection hypothesis. For example, if an older brother donates his organs for his younger brother, it’s difficult to explain this behavior by simple brotherly love alone. Applying the hypothesis of kin selection, it can be interpreted as an act of protecting and spreading one’s own genes by helping the younger sibling because they share the same genes. In this context, many forms of altruistic behavior that occur within families can be better understood through the kin selection hypothesis.
However, not all altruistic behaviors in nature can be explained by the kin selection hypothesis. Take, for example, the meerkat population. When meerkats forage for food, they bury their heads into the ground. While their heads are buried, they are defenseless against predators. When a foraging meerkat is defenseless, one or two other meerkats from the same group will watch over it. The watchers alert the other meerkats to the presence of a predator by making a loud alarm call. These alarm calls make the meerkats easy targets for predators, so meerkats’ use of the net is a selfless act of individual sacrifice. The existence of kinship between individuals in a colony has been used to explain this behavior, and like bee colonies, the altruistic behavior of meerkat colonies has been used to support the kinship selection hypothesis. However, Tim Clutton-Brock of the University of Cambridge found that meerkat networking was not a good candidate for the kinship selection hypothesis. When Clutton-Brock studied a group of meerkats, he found that the members of the group were mixed with outsider meerkats who were not related to any of the other members, and he found that there was no difference in the number of retrievals per individual between the retrievals of related meerkats and outsider meerkats. This means that the altruistic behavior of “lookout” in meerkats cannot be conclusively attributed to gene sharing, and the kin selection hypothesis is limited in its ability to explain all altruistic behaviors. Furthermore, the discovery that some species with “inter-individual gene sharing,” such as bee colonies, exhibit altruistic behavior among kin, while other species do not, and that altruistic behaviors such as donations between people who are not related by blood occur in human societies, makes it clear that kin selection is not a necessary or sufficient condition for all altruistic behavior.
Furthermore, altruistic behavior between unrelated individuals is frequently observed in human society. For example, anonymous donors and volunteers act to help others regardless of their own interests. These behaviors are not fully explained by the kin selection hypothesis alone. In such cases, other motivations may come into play, such as psychological satisfaction or social prestige. Therefore, understanding altruistic behavior requires a multidisciplinary approach.
So far, we’ve discussed one powerful theory that explains many of the altruistic behaviors we see around us, the kin selection hypothesis, and its limitations. While the kin selection hypothesis adds depth to our biological understanding by looking beyond the individual and explaining altruistic behavior in terms of genes, it also has clear limitations and falls short of fully explaining all altruistic behavior. As such, we must recognize that we need to consider other theories in addition to the kin selection hypothesis to understand altruistic behavior in organisms. By understanding altruistic behavior through multiple lenses, we can gain a richer and more accurate picture of life’s behavior.
